Tesler - A Personal History of Modeless Text Editing and Cut-Copy-Paste

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Timelines provides perspectives on HCI history, glancing back at a road
that sometimes took unexpected branches and turns. History is not a dry list
of events; it is about points of view and differing interpretations.
Jonathan Grudin, Editor
A Personal History of Modeless
Text Editing and Cut/Copy-Paste
Larry Tesler
i n t e r a c t i o n s J u l y + A u g u s t 2 0 12
Consultant | tesler@nomodes.com
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Larry Tesler’s vision of interaction
design process has inspired many
designers, developers, and researchers.
His leadership in early graphical user
interface successes led to his receiving
SIGCHI’s Lifetime Practice Award in
2011. —Jonathan Grudin
I have been a computer programmer for more than 50 years. From
the beginning, I was annoyed by
software that made life harder
than necessary for users. I got to do
something about it as a student at
Stanford University and in a variety
of subsequent engineering, user
experience, and management roles
at Xerox PARC, Apple, Amazon.com,
and Yahoo!
The best known of my contributions is cut/copy-paste. I developed
the pattern over a period of years
in collaboration with a series of
colleagues. But cut/copy-paste was
not a distinct project; it was one of
a collection of graphical user interface (GUI) patterns I called modeless
text editing.
I was not the first person to notice
the ill effects of modes on error
rates. Nor was I the first to try to
eliminate the most onerous modes.
But for me, mode reduction became
a research endeavor and a business
mission. I helped to develop the
theoretical underpinnings of modeless editing and the first products to
affirm the validity of the theories.
The 1960s
In 1960, while a student at the
Bronx High School of Science, I
learned a FORTRAN-like language.
I loved its power, but its unintuitive
restrictions frustrated me.
In 1961, I entered Stanford
as a freshman. In 1962, I made
usability improvements to a pioneering animation language.
That project gave me experience
with discount usability studies
and participatory design [1].
Soon, word got around that I
was a pretty good programmer
who made software easy to use.
Professors and grad students alike
asked me to consult. In 1963, I
founded a contract software company that was one of only six in the
Palo Alto Yellow Pages.
During the 1960s, interactive
time-sharing began to displace
batch, and pointing devices became
common on mini-computers. I
much preferred interactive to
batch, but most interactive programs had modes, which always
tripped me up. I began to analyze
command languages to root out the
causes of modes and mode errors.
In 1968, I began working at the
Stanford Artificial Intelligence
Laboratory (SAIL) for Ken Colby, a
psychiatrist and cognitive scientist.
Colby had developed PARRY, a conversational program that simulated
a paranoid patient. While working
on his team, I got to know Alan
Kay, Don Norman, Terry Winograd,
and David Canfield Smith—all of
whom became HCI pioneers—and
I learned a little about cognitive
psychology.
In early 1969, I visited Doug
Engelbart’s Augmentation Research
Center at SRI in Menlo Park,
California. Engelbart had recently
given the first public demonstration
of NLS (oN Line System), a visionary prototype built on a time-sharing system [2]. The groundbreaking
event became known as “the mother of all demos.” Among the innovations that debuted were the mouse,
tiled windows, multiple views,
outlining, hypertext, collaborative
editing, and videoconferencing.
From 1968 to 1970, I sometimes
pasted up a quarterly catalog for
a local nonprofit. While “cutting
and pasting” with blades and glue,
I imagined an interactive page
makeup system that would simplify
the process.
During the same period, Pentti
Kanerva showed me his PDP-10
port of Brian Tolliver’s full-screen
text editor, TVEDIT. Kanerva had
added a simple error-recovery
command called oops. He had also
added a two-step move: The delete
step moved user-specified text
to the top of a stack; the retrieve
Timelines
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How Modes
Degrade Usability
The 1970s
In 1971, Les Earnest, director of
the A.I. Lab, asked me to design
and implement a page-makeup
language that could number sections and generate an index, table
of contents, footnotes, crossreferences, and so on. I proposed
to make it interactive, but he
wanted a batch system, which
I admitted would be easier.
In a few months of intense work,
I created PUB: The Document
Compiler [3]. PUB was a markup
language with embedded tags and
scripting. It became popular among
graduate students at ARPANETconnected universities.
In 1973, I joined Xerox Palo
Alto Research Center (PARC) as
a member of the PARC Online
Office System (POLOS) team but
spent some of my time working on
Smalltalk with Alan Kay’s Learning
Research Group. One reason I was
interested in working with Kay was
that his invention of overlapping
windows was motivated by a desire
to find alternatives to modes.
Most members of the POLOS
team had come to Xerox from
Engelbart’s group at SRI. My
manager, Bill English, had
been involved in the design
of the mouse, co-authored
Engelbart’s 1968 paper, and managed the famous NLS demo.
From its inception, NLS was used
mainly to construct and revise
technical specifications, source
code, and other indented outlines.
Its regular users found it a good fit
for that. But I felt that it would not
gain public acceptance as a tool for
editing common documents such
as letters, memos, and forms. Its
command language had numerous modes. Outside text-entry
mode, virtually every keystroke
and click changed the mode.
The syntax of the NLS command
language evolved over time, but it
was always prefix, in which the verb
is specified before its object (see
Figure 1 and sidebar: “How Modes
Degrade Usability”). To delete a
paragraph, you told NLS to delete
before you told it what paragraph it
should delete.
Clicking the mouse button when
the pointer was over something
was called marking. Three frequently used NLS commands that
required marking were:
In a 1981 article about Smalltalk [9], I defined a mode
as “a state of the user interface that lasts for a period of
time, is not associated with any particular object, and has
no role other than to place an interpretation on operator
input.” Three properties of a command language that
cause mode-related problems are:
• Verbs precede their objects. The most frequently used
commands in many interactive systems involve a verb
and one object. If the language has any consistency at
all, there is prevalent command syntax, which is usually
either prefix or suffix. The distinction is whether the user
specifies the verb before or after its object. Suffix syntax
has a usability advantage: When the user specifies the
verb last, its object has already been specified, and the
command can be executed immediately. Systems that
use prefix syntax must enter a mode to wait for the user
to specify the object. Keeping track of mode changes can
distract a user from the task at hand.
• Key meanings are mode-dependent. Languages that
use unmodified letter keys to do anything but enter
those letters as text need at least two modes: text and
command. If unmodified letter keys are typed in command
mode but the user thinks the system is in text mode,
D(elete) W(ord) <mark
affected word> <ok>
unintended and sometimes disastrous results ensue.
M(ove) T(ext) <mark source
text start> <mark source text
end> <mark destination> <ok>
in a mode. An oft-heard question is, “How do I get out of
I(nsert) S(tatement) <mark
destination> <type text to
insert> <ok>
The command-accept action,
symbolized here by <ok>, could be
invoked from either the keyboard or
the mouse. Text was an arbitrary
span of text. A statement was usually a paragraph.
As the user typed and clicked,
pieces of a command line accumulated in a visible window. The user
could remove the newest piece of
the command line from the window or erase the whole line and
start over. When the user invoked
<ok>, NLS erased the whole line,
preventing further modification.
• Mode escapes are inconsistent. Users often get “stuck”
this mode?”
Then it performed the command.
Because move was a single command, both the destination and the
source had to be visible onscreen
before typing “M.” The same restriction applied to copy and replace.
Features such as collapsible outlines provided ways to circumvent
the restriction, but the user had to
learn more syntax and plan ahead.
I believed that competitors would
surpass Xerox in speed of learning and ease of use if we stayed
with NLS syntax. Most of my colleagues were unconcerned. They
considered NLS intuitive because
of its English-like verb-object
grammar. The syntax allowed a
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step moved the top element of the
stack to a user-designated location.
Between steps, the user could do
anything that left the stack intact,
including filing, searching, typing,
and moving other text. Although
TVEDIT had modes, it seemed to
me that a two-step move and an
oops-like error-recovery command
could help to make a suitably
designed editor modeless.
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•F
igure 1. NLS prefix
syntax, simplified.
Timelines
verb
Delete
Move
Insert
Replace
noun
mark
Character
Word
Statement
Text (2 marks)
mark
type
•F
igure 2. Modeless
suffix syntax.
Click
Click & Drag
•F
igure 3. Error
recovery with NLS
prefix syntax.
verb
verb
object
noun
mark
verb
select
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type
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Cut
Paste
typing
Backspace backs up one step.
Command Delete starts over.
•F
igure 4. Error
recovery with modeless suffix syntax.
OK
lot of room for growth. And the
command line made it possible to
use NLS from older terminals.
During my first week on the job,
Bill English asked me to work with
another new hire, Jeff Rulifson, to
develop a vision of the future of
editing. Rulifson and I met several times to brainstorm. When
OK
mark
type
Selection error? Reselect.
Command error? Undo.
I confided my concerns about
the NLS command language, he
revealed that he had designed it.
He had meant it to serve as a temporary tool for software testing.
Engelbart’s team had run usability
studies and made incremental
improvements, but they had not
seriously considered suffix syntax,
in which the verb is specified after
its object (see Figure 2 and sidebar:
“How Modes Degrade Usability”).
I told Rulifson about the errorrecovery advantages of suffix syntax (see Figures 3 and 4), namely:
• If the user made a selection
mistake while specifying the object,
she could simply select again.
There was no need to back up in
the command line. There was no
need to display a command line.
• If the user chose the wrong
verb, the consequences became
immediately visible. To correct the
mistake, she could invoke an operation that undid the command.
I had not previously seen an
error-recovery command more general than TVEDIT’s oops. Rulifson
told me about one that our PARC
colleague, Warren Teitelman, had
introduced in his user-friendly LISP
shell. It was aptly named undo. And
it became our model.
Rulifson and I also discussed
the use of graphics in interfaces.
He had recently read a book about
semiotics that defined an icon as a
labeled pictogram and mentioned
its potential relevance to interactive computing.
We circulated a few versions
of a white paper around PARC.
It was entitled “OGDEN: An
Overly General Display Editor
for Non-programmers.” We proposed iconic user interfaces
with desks and file cabinets. We
also proposed modeless postfix syntax with cut and paste.
Rulifson’s willingness to turn
the user interface he had designed
for NLS on its head made it much
easier to get the rest of the POLOS
team to consider my proposals.
With the help of Barbara Grosz, I
ran user studies, including blankscreen studies, which laid bare the
problems that modes caused [4].
Then, using a very early version of
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Objections to Modeless
Editing and Cut/Copy-Paste
the Smalltalk language, I developed
a simple, typewriter-like editor with
very few modes. People who had
never touched a computer were
able to learn the simple editor in
five minutes.
Objection 1. User mistakes. After performing a cut, the user might forget that important text was in
what we now call the clipboard. She could lose it by cutting or copying something else without an
intervening paste or undo.
Response: The ability to do other things between cut and paste entails more benefits than risks.
Response: A suitable undoing or versioning facility will allow recovery of accidentally deleted data.
Objection 2. Implementation cost. When the user invokes cut or copy, then closes the source document
before specifying the destination, the software has to retain a copy of the cut or copied material in the
clipboard along with fonts, graphics, and so on, just in case a subsequent paste required it.
Response: This was a major concern from 1975 to 1982 because early personal computers had
so little DRAM and disk space. But we knew that Moore’s Law would soon provide us with enough
memory and processing speed to hold on to most clipboards.
Response: It is better to burden the developer than the user. A decade later, I turned this argument into
the Law of Conservation of Complexity: Every system has an irreducible amount of complexity; the
only question is, who is going to have to deal with it? The user? The application programmer? Or the
platform developer?
Objection 3. Speed. If you were to watch an NLS expert edit a document, you’d see his fingers blazing
and hear a drumroll of strokes (mouse clicks and key presses). Observe an expert user of a modeless
editor and you’ll hear fewer strokes per unit time. Staccato versus legato. Citing Fitts’s Law, some NLS
advocates claimed a speed advantage and attributed it to less hand motion.
Response: Stu Card and Tom Moran showed that the command syntax of NLS required more strokes
than that of Gypsy, sometimes twice as many, and in some cases, more mental preparation time. A
1981 study by Terry Roberts and Moran compared experienced users of Gypsy to experienced users
of NLS and six other well-known editors [13]. The authors found that experienced Gypsy users, on
average, performed a benchmark set of tasks in less time than users of the other editors and twothirds the time of NLS. Fewer key and button presses were required.
Objection 4: Lack of extensibility. Modes can be removed from text editors, but it is hard to remove the
modes from other types of software, such as graphics.
Response: In the study cited above, the one measure by which Gypsy trailed other text editors was
functionality. But that finding didn’t prove that the modeless model could not be extended, only that
it had not been extended. Another decade elapsed before Apple’s Macintosh entered the market
and attracted enough applications to prove the model extensible. As for graphics editors, I agree
with the common wisdom that modes can be good when they support a metaphor like picking up
a brush, and when feedback identifying the current mode is displayed where the user is almost
certain to be looking.
filing system that supported versions and drafts. The software
took a few months to complete.
Gypsy introduced several modeless user interface features that are
now standard [7]. The user could:
• click between characters, see a
blinking insertion point appear, and
start typing;
• down-drag-up to select text;
• double-click a word to select it;
• move text in two steps called
cut and paste;
• copy text in two steps called
copy and paste; and
• to search, type or paste the
search text into an editable field.
When we began implementa-
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Gypsy
English commended my work but
asked me to turn my attention to
the POLOS system. I had barely
started to do that when serendipity struck. Ginn and Company, a
textbook publisher owned by Xerox,
asked PARC to build two applications, one for galley editing and
one for page layout. English knew
I’d be interested and asked me to
run the project. He assigned Dan
Swinehart to advise me. Swinehart,
whom I had worked with at SAIL,
was a passionate opponent of
modes and a fount of wisdom.
My suggestion to use cut and
paste in both the page-makeup system and the galley editor delighted
Ginn management. I now had a
receptive audience for my experiments.
In another welcome turn of
events, Ginn hired a software engineer named Tim Mott to conduct an
ethnographic study at their facility
near Boston. In 1974, after completing the study, Mott came to PARC to
help me implement the galley editor,
which he dubbed Gypsy. By the time
he arrived, several Xerox Alto personal computers were in operation.
Charles Simonyi and Tom Malloy
had gotten an early version of the
Bravo text editor running on Alto.
Bravo was a pioneering WYSIWYG
application, the brainchild of Butler
Lampson and Simonyi [5,6,7].
To implement Gypsy, we
took Bravo’s source code and
replaced the modal user interface with a modeless one. At
Ginn’s request, we added bold,
italic, and underline type and a
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Timelines
Gypsy
Smalltalk
BravoX*
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•F
igure 5. The path
to ubiquity.
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Woodstock
Star*
LisaWrite
MS Word
Mac
Windows
Bus. Week
iOS
* Modeless insert but no cut/copy-paste
tion, I didn’t have all the details of
the interface worked out. I figured
we would iterate as we developed.
What I didn’t count on was Mott’s
creativity and how attuned he
was to the target users he had
observed at Ginn. For example,
when none of my proposals for
word selection panned out, it was
he who came up with the idea of
double click. Lesson learned: You
don’t have all the answers. Team up.
During the development of
Gypsy, PARC hired Tom Moran, Stu
Card, and Beverly McHugh. They
observed me running a usability
study and offered to run future
studies for us. The studies Beverly
ran were invaluable in refining
the user interface of Gypsy. Lesson
learned: Some people can do what you
do better than you can. Team up.
When Gypsy was finished in
early 1975, Mott brought it to Ginn.
The users loved its strengths.
But they disliked its weaknesses,
especially the almost complete
absence of code maintenance,
an engineering requirement we
researchers had neglected. Lesson
learned: If you are going to give your
research prototype to users who may
grow to depend on it, be sure that
someone has planned for maintenance.
Influences
In June of 1975, Businessweek published a feature article called “The
Office of the Future” that mentioned Gypsy. It also mentioned cut
and paste, but only in the context
of Woodstock, an office-system prototype that Swinehart had developed as he advised us on Gypsy.
Other PARC colleagues built on
our work. Mott and I had used dedicated keys for cut, copy, paste, and
undo. Inspired partly by William
Newman’s use of pop-up icon grids
in his Markup painting program
[8], Dan Ingalls implemented a
delightfully simple pop-up menu in
Smalltalk that contained a column
listing the four command names
[9]. That menu evolved into the
right-click contextual menus that
are commonplace today. Lesson
learned: When you think it’s as simple
as it can be, there is probably a way to
make it even simpler.
Gypsy also influenced BravoX
and the Xerox Star. BravoX was a
successor to Bravo that Simonyi
developed at PARC. Star was the
first commercial office system with
a mouse, bitmapped display, windows, and file servers. Star had a
thoroughly consistent and nearly
modeless user interface [10].
Both BravoX and Star supported
modeless “click and type” insertion, but neither used a two-step
cut/copy-paste. The user could
perform a move or copy with
fewer strokes than Gypsy—two in
one version of BravoX and three
in Star, versus four in Gypsy. But
the trade-off to achieve fewer
strokes was a mode that limited
what the user could do between
source and destination selection.
In the early 1980s, Xerox’s
modeless editors influenced
Apple’s Lisa and Macintosh as
well as Microsoft Word, Office,
and Windows. The popularity
of Microsoft and Apple products
made cut/copy-paste and modeless text editing ubiquitous, even
reaching smartphones with multitouch screens (see Figure 5).
There are still some modes in
modern word processors, such
as the format paintbrush in
Microsoft Word. And designers
still experiment with alternative ways to move text, such
as drag-and-drop in Word. But
these are shortcuts that uninterested users can usually ignore.
Post-Gypsy
After Mott returned to PARC
from Ginn, he joined a different
project. Next up for me was the
page-makeup system that Ginn
had requested. I used Smalltalk to
build a prototype called Cypress.
After the user made a selection, an
edit menu would pop up automatically nearby, as on today’s iPhone.
Timelines
The 1980s
By 1980, Xerox’s copier patents had expired, and the company was fighting for survival.
It became clear that we were
not going to bring much PARC
work to market except the laser
printer and the STAR, both
aimed at business users.
I went to Apple to work on the
Lisa user interface and applications. To develop the Lisa User
Interface Standards [11], I teamed
up with the multitalented Bill
Atkinson, who shared my insistence on simplicity. For a few weeks
that summer, he would build a
prototype almost every night, and
I’d run a usability study the next
morning. Jef Raskin, who was
beginning work on a concept he
called Macintosh, was skeptical
about the mouse but generously
offered suggestions and support.
The Lisa software engineers internalized modeless editing principles
and found clever ways to make
their applications modeless. My
job was to manage them and make
evidence-based decisions about the
design of the interface [12].
One of many contributions the
Lisa made to the GUI was the
dialog box, a vehicle for providing parameters to a modeless
command. Rod Perkins designed
Lisa dialog boxes. The typical
dialog prevented the user from
continuing work while it was
open. That made it modal. But
the widgets within the dialog
could be operated in any order,
making it locally modeless. And
the mode escape was performed
in a consistent way, by clicking
dismissal buttons that were consistently located and labeled.
At Apple, as at PARC, the new
user interface had its skeptics,
some of whom preferred the
NLS style of interface. But Apple
wanted products. “Religious wars”
did break out, but they couldn’t
last more than a few days. Lesson
learned: If you need to fight an
uphill battle, choose a short hill.
Acknowledgements
I am grateful to William Newman,
Bill Duvall, Stuart Card, Charles
Simonyi, Jeff Rulifson, Terry
Roberts, Charles Irby, and Tom
Malloy for reviewing drafts and
providing factual corrections
and insightful perspectives. Any
remaining errors are mine.
Today
In the 1970s, move and copy were
edits that users wanted to perform
and cut/copy-paste was a new way
for users to perform them. Now
these terms have reversed roles.
Users don’t say they want to “move”
things; they say they want to “cut
and paste” them. Even scholarly
writings about Star, NLS, and other
systems with modal moves often
refer to their move/copy operations
as cut/copy-paste.
Before the computer age, the
term cut and paste was publishingindustry jargon. The term copy and
paste appears to have originated
in Gypsy. Both terms are widely
understood today. I don’t know who
coined copy-paste job or copy-paste
error. But when I make a copy-paste
error, unlike most people, I have
nobody else to blame.
9. Tesler, L. The Smalltalk environment. Byte 6, 8
(Aug. 1981), 90-147.
EndNotes:
1. For more information on this project see my 2011
CHI Lifetime Practice Award talk (particularly minutes
6-12); http://dmcc.acm.org/pres/?query=/dmcc///
confdata/chi2011/220-221-222/2011-05-11_09h02
2. Engelbart, D.C. and English, W.K. A research
center for augmenting human intellect. Proc. AFIPS
Conference (Dec. 1968), 395-410.
3. The manual is on my website: www.nomodes.
com/pub_manual.html.
4. For study notes, please see http://nomodes.
com/Larry_Tesler_Consulting/1973_User_Study_
Notes.html
5. Lampson, B. Bravo Manual. Alto User’s Handbook.
Xerox Palo Alto Research Center, 1976, 26-60.
6. Newman, W. Design case study: The Bravo text
editor. interactions 19, 1 (Jan. + Feb. 2012), 75-80.
7. Lampson, B. Personal distributed computing:
The Alto and Ethernet Software. Proc. of the ACM
Conference on the History of Personal Workstations
(Jan. 1986).
8. Newman, W.M. Markup Manual. Alto User’s
Handbook. Xerox Palo Alto Research Center 1979,
85-96.
10. Smith, D.C., Irby, C., Kimball, R., Verplank, W.,
and Harslem, E. Designing the Star user interface.
Byte 7, 4 (Apr. 1982), 242-282.
11. Atkinson, B. Lisa User Interface Standards.
Apple Computer, Inc., 1980.
12. Perkins, R., Keller, D.S. and Ludolph, F.
Inventing the Lisa user interface. interactions 4, 1
(Jan. 1997), 40-53.
13. Roberts, T.L. and Moran, T.P. The evaluation
of text editors: Methodology and empirical results.
Communications of the ACM 26, 4 (Apr. 1983),
265-283.
About the Author
Larry Tesler is a freelance consultant in Silicon Valley. He was formerly a member of the research
staff at PARC, the chief scientist
of Apple, and a user experience
vice president at Amazon and
Yahoo! This article is based on the Lifetime Practice
Award talk he delivered at CHI 2011.
DOI: 10.1145/2212877.2212896
© 2012 ACM 1072-5220/12/07 $15.00
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Implemented in Smalltalk-76, the
Cypress prototype ran so slowly
that to demonstrate it, we shot
video at three frames per second
and played it back at 30fps.
By then, Xerox’s priorities had
changed, as had my personal
interests. Ginn agreed to wait a
few years until they could do page
layout on a well-maintained commercial system. I developed the
Smalltalk Browser, an ancestor of
today’s IDE’s (integrated development environments). Outside work
hours, I dabbled in hobby computers and developed educational
applications for the Commodore
PET. Then, in December of 1979,
Steve Jobs paid a world-changing
visit to PARC and I began rethinking my career.
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